In meatspace I'm a Software Engineer in Test, which means I write automated testing as my day job.

I was wondering if my experience could be utilized here? Having good unit tests is always of help in a project, especially as it nears "completion", and they're critical to the success of major refactors. Obviously I'm referring to post-1.0 de-hardcoding there.

Now, the trouble is that a lot of refactoring will probably be necessary just to make the project unit testable. Working Effectively with Legacy Code by Michael C. Feathers is a fantastic book on such things, by the way. The stickiness of that is partially mitigated by the fact that we'll have unit tests to confirm that the refactoring worked!

I'm not ready to jump in on such a project right now, but I'd like to gauge interest anyway.

I don't think tests never failing means they were a waste of time. Good tests and wide coverage does a lot to increase code confidence, both for the person writing the test and everyone who follows after.

I'd argue this is more important for open source projects, where you have less people familiar with the whole thing and new people rotating in all the time. I'd feel much better jumping into a new, unfamiliar project if it was already well-tested.

That's only true with TDD, and TDD is basically incompatible with how game engines need to be designed. Typically, to me, when I see a small number of tests and they never get triggered, that tells me that the project doesn't do enough regression testing - but this is a game engine, so going ingame and making sure that it works close to intended is basically a rigorous regression test itself.